Microfluidic devices and systems for performing blood tests and tests on other types of biological fluids are widely known and are used for performing tests of different types, such a coagulation tests e.g. for determining the coagulation rate in a blood sample or agglutination tests e.g. for determining blood type of a blood sample.
Devices and systems for performing blood tests using an optical detector for determining a change in the blood sample due to a reaction with a reagent. Such systems and methods for performing optically based blood tests are e.g. disclosed in U.S. Pat. No. 4,034,601 (American Hospital Supply), which discloses a method and apparatus for measuring coagulation on blood on a filament. A filament strip is drawn through a blood sample mixed with a clotting reagent until a clot is detected. The coagulation time until clotting is optically measured.
U.S. Pat. No. 5,167,145 (David M Butler et al.) describes a method recording the clotting time of whole blood as it proceeds from fibrinogen through known stages of coagulation, culminating in the cross-linking of the fibrin clot which ultimately solidifies and dries at the end of a cycle, including the steps of:
providing a measured sample of whole blood to be tested;
transmitting infrared electromagnetic energy through the blood sample;
detecting the transmission of the infrared energy and electronically producing the signals in response to said infrared energy; and
measuring a peak transmission level of said infrared energy and calibrating said peak signal in terms of clotting time of said whole blood sample whereby the clotting time is represented by the peak transmission level of the infrared energy through the whole blood sample.
US 2002/0110922 (Bozicevic) describes a method of recording the clotting time of whole blood in a fluid device. Blood is introduced in the flow device, react with a coagulation reagents, and proceed to fill a measuring chamber where flow is stopped by a stop junction. Formation of a blood clot is measuring using an optical detector—blood clotting result in reduction of transmission. A similar method is described in WO 2004/044560.
U.S. Pat. No. 6,488,896 describes a method and a microfluidic device to determine optically if any agglutination and or coagulation take place or not. Time for the reaction is not measured.
U.S. Pat. No. 5,534,226 (International Technidyne) describes a method and a micruflidic device to determine if any agglutination and or coagulation takes place the time is measured by measuring its presents in specific zones and by using CPU chip linked to a timer (clock)
WO 2006/042332 (FASTRAQ) describes a method and a microfluidic device for performing a immobilization test on a biological fluid such as blood or urine. The device is arranged for controlling flow rate to adjust incubation time. Optical means may be used for detecting progress of events, such as sample introduction.
The prior art devices and methods for testing fluid samples using an optical detector basically determine a change in the fluid sample by a corresponding change in light absorbance/reflection at certain wavelength.